1. Field of the Invention
The present invention relates generally to a power supply circuit for headlamps mounted on automotive vehicles. More specifically, the invention relates to a power supply circuit in which a pair of headlamps can be selectively connected to a power source in series or parallel to decrease or increase luminous intensity thereof.
2. Description of the Prior Art
Such a power supply circuit is described in the Japanese Utility Model First Publication (Jikkai) Showa 59-118648. This circuit comprises a pair of headlamps, a battery, a manually operable switch and a relay which can selectively establish communication between the battery and the headlamps in series or parallel. Each of the headlamps comprises low-beam and high-beam filaments. In this circuit, the headlamps are connected to the battery in parallel via the relay when the switch is OFF so that luminous intensities of the headlamps are relatively high. In response to turning ON of the switch, the headlamps are connected to the battery in series via the relay, so that the intensities can be decreased. In addition, each of the headlamps is provided with a fuse. When the headlamps are connected to the battery in series, the electricity runs through only one of the fuses which is provided near the battery. Therefore, if the connection between the other fuse and the high-beam filament is open, undesirable current drain may occur, so that other electronic parts may be broken.